The present application is based on the disclosure and teachings of the following applications: U.S. provisional patent application No. 61/547,186 filed on Oct. 14, 2011; U.S. patent application Ser. No. 13/650,438 filed on Oct. 12, 2012 a.k.a. US publication No. 2014/0,104,222; U.S. patent application Ser. No. 13/650,649 filed on Oct. 12, 2012 a.k.a. US publication No. 2013/0,038,573; and U.S. patent application Ser. No. 13/650,683 filed on Oct. 12, 2012 a.k.a. US publication No. 2013/0,038,574.
In the present application, the term “touch panel” is used to encompass both a touch screen and a touch panel. Referring to FIG. 1, a schematic diagram illustrating electrodes of a touch panel 100 is shown in the upper half (a) of the drawing. The touch panel 100 includes a plurality of first electrodes 110 and a plurality of second electrodes 120. The first and second electrodes form a plurality of intersections. A touch sensitive processing apparatus is connected to the plurality of first electrodes 110 and the plurality of second electrodes 120 for performing various driving and sensing processes. In an embodiment, the touch panel 100 also includes shielding electrodes (not shown).
Based on the disclosure of the above applications, the touch sensitive processing apparatus may simultaneously drive all of the first electrodes 110, or even the shielding electrodes, and perform sensing based on the mutual capacitive coupling signals of all of the second electrodes 120. When a conductive liquid is covering a small area of the touch panel 100, it may cause the sensing values to reflect positive-touch and negative-touch information. If the sensing information only includes negative-touch information but not positive-touch information, then it can be determined that the touch panel 100 is covered by the conductive liquid. When positive-touch information exists on the edge of negative-touch information, then it can also be determined that the touch panel 100 is covered by the conductive liquid. When the touch panel 100 is covered by a conductive liquid, the touch sensitive processing apparatus may initiate several responses; for example, it may warn the operating system to ignore the area covered by the conductive liquid and refrain from reporting touch/proximity events within that area, or stop the touch sensitive processing operations.
In addition to an area covered by a conductive liquid being too large, there is the possibility that a large conductive object is placed on the touch panel 100, covering many of the intersections. For example, a modern induction cooker may use the touch panel 100 as an input. However, a user may accidently place an iron pan or other cooking utensils on the touch panel 100, or boiling water on the induction cooker may have spilt onto the touch panel, which may lead to misjudgments of the touch sensitive processing apparatus. If the result of a misjudgment is to turn on or increase the power of the induction cooker, serious accident or dangerous situations may occur.
Therefore, a method and apparatus for detecting if a touch panel is mostly covered by a conductive object is needed and can be used to detect if the touch panel is covered by a conductive object or liquid more than a certain percentage, which can be used in turn to disable reporting of touch points or to adopt another touch sensitive processing method if it is the case. Moreover, a touch sensitive processing method and apparatus that allows one-finger operations and two-finger scaling operations on a touch panel that is mostly covered by a conductive object.